Double clutching and heel-toe?

[WATAJK]

LOL

shit man, now me and the mad scientist have to rip apart the block, and replace the....(wait for it).....PISTON RINGS YOU FRIED!

can double clutching be bad for your car?

IF you do it correctly no.
If you do it incorrectly yes.

Same issue as quick shifting.
Doing it properly its awesome as you can go from first to second (whichever gear doesnt matter) in the matter of a second not even..
IF not done properly you run the risk of scratching your gear box n mis-shifting